“…Most observations on the relative solubilities of the oxides or hydrous precipitates in acidic solutions have been only qualitative, although Brauner (45) early pointed out that the solubilities in aqueous ammonium nitrate solution of Di205, Di203, and La203 were in the ratio of 1 to 10 to 29. More recently Prandtl and coworkers (335,342,343,344,345,346) have measured the solubilities of a number of hydroxides in ammonium salt solutions in the presence and absence of cations forming ammonia complexes. (and basicity increases) in the order yttrium, samarium, neodymium, praseodymium, lanthanum.…”